“The polar vortex can stretch like the recent event or even break in two like more severe cold snaps in the 80’s and 90’s. The solar activity (high or low) does not cause anything directly.”
Some people believe differently. http://www.youtube.com/watch?v=1ivcycdvO1A&feature=c4-overview&list=UUTiL1q9YbrVam5nP2xzFTWQ
What the guy in that video says does not conflict with what I said which is that low solar activity doesn't cause anything directly (nor high activity).
He is showing the 300 mb jet on that video not the vortex at 10 mb. The Vortex is simply a low pressure in the stratosphere and he is correct at the end when he says "continuity with the upper stratospheric flow". The jet he shows does feedback to the vortex and the vortex can then coincide with a dip in the jet if it is broken by a vertical intrusion from that same jet. But they are not the same thing.
It is true that the SSW's are more likely at times of low solar activity (e.g. the largest ever was Jan 1997) they also take place with medium activity (e.g. Jan 84 mentioned above). Again, there is no direct cause and effect, just a tendency for low solar activity to result in uneven heating the stratosphere and thus a tendency (but by no means a certainty) of these types of events. They are simply terrestrial weather which overrides any effect the sun has or human CO2 for that matter.